Nowadays we say everything is already invented! There's little or no space to create something absolutely new. Same here...
Watch Dogs deliver's a GTA experience and that's a fact.
However, it does the job well. Unique characteristics make it a one of a kind game. Not being absolutely brilliant as it's prime matter it delivers a solid gaming experience, with various twists and turns that make you distance a bit from GTA. Brilliant graphics on the PS4 - although I believe it could be better if not on 3rd generation systems - and a fluid and "arcade-ish" game play, Watch Dogs does it's job well.
What could improve? A lot indeed! No helicopters or aircrafts available for a ride and very limited and quality lacking soundtrack are the top fails but the confusing storyline may also be a setback for the players who endure on that aspect of games.
Overall it entertained me for about a month with a couple of days per week playing it. Made me feel playing GTA on the PS2 again back when I was 16. Not so immersive but a good quality game for a first on the PS4!